It is known that the characteristics of certain kinds of dielectric fluids vary when the dielectric fluids are subjected to electric fields. In case of liquid crystals, for example, when a voltage is applied to liquid crystal compounds in a liquid crystal phase (i.e., intermediate phase between a solid phase and a liquid phase), orientation properties of the compounds are controlled to thereby adjust light transmittance of the compounds, whereby visible images are formed. However, even if the liquid crystal compounds regulated by the orientation plates are placed in electric fields, they cannot flow freely because they are not liberated from the regulation.
Also, some fluids are known to exert an effect of variation of properties such as viscosity (electrical rheology effect or Winslow Effect).
The fluids exerting electrical rheology effect or Wien effect are generally colloidal dispersions wherein solid components, such as silica gel, cellulose, casein and polystyrene ion exchange resins, are mixed with insulating oils and dispersed in the oils, so that the storage stability of such fluids is low.
As lubricating oils for automobiles, those exhibiting electrical rheology effect have been proposed, but such lubricating oils are also heterogeneous and have a problem of low storage stability.
In Japanese Patent Laid-Open Publications No. 57274/1994 and No. 73390/1994, inventions of electrosensitive compositions wherein insulating oils are blended with specific fluorine compounds are disclosed.
The compositions disclosed in those publications are mixtures of insulating oils and fluorine compounds, and therefore they have a problem in the storage stability. Additionally, there is a worldwide tendency to avoid the use of fluorine compounds in recent years.